Virtual tours have become a frequently used technique for providing viewers with information about scenes of interest. Such tours can provide a photorealistic, interactive and immersive experience of a scene or collection of scenes. These tours can incorporate one or more of a wide variety of graphic display techniques in representing the scenes.
One effective technique for presenting information as part of these tours is display of a panorama or panoramic image. Panoramic viewers can display images with wide fields of view, while maintaining detail across the entire picture. Several steps are required for creation and display of these panoramas: image capture, image “stitching”, and panorama display (or viewing). The first step is capturing an image of the scene 100, which is also known as the acquisition step. Multiple photographs are typically taken from various angles from a single position 110 in space, as shown in FIG. 1. Regular cameras and equipment may be used and specialized hardware is not usually required. The photographic images taken are then “stitched” together using stitching techniques, as are known in the art, to provide a substantially seamless view of a scene from a given position. FIG. 2 shows an example of a scene in two panoramic formats: a sphere map 200, 220 and a cube map 210, 230. The unwrapped stitched image 200 maps onto a spherical geometry 220, and the panorama virtually replicates the photography acquisition position when viewed from the center of the sphere. The process works similarly with cube map panoramas. Other types of panoramic projections may be employed, but the process is similar. Note that images may be thought of as partial panoramas. The final step is display of or viewing the panorama, as illustrated in FIG. 3. The stitched together images are viewed interactively using panorama-viewing techniques, as are known in the art. In FIG. 3, the acquisition position 310 in virtual space in the center of the sphere is shown for a spherical panorama 300. Also shown is the pin-hole camera projection frustum 320 that represents one portion of the panoramic image that may be viewed on the display.
Current panoramic virtual tours have significant limitations. The inherent nature of panoramas (including regular photographs and images), is that panoramas are taken from a single acquisition position, and, thus, the images are static. To describe a broader area, i.e., beyond a view from a point in space, panoramic virtual tours typically employ a “periscope view”—the end user “pops” into a point in space, looks around, and then instantaneously “pops” into another position in space to navigate through a wider area. Assuming a simple case of two panoramic scenes, even when the acquisition positions are very close, it is often difficult for the viewer to mentally connect the two scenes. The two panoramas are not inherently capable of describing how the panoramas are connected and oriented with respect to each other. With these limitations, it is difficult for the viewer to understand the space, sense of orientation, and scale of a wider area with current virtual tours.